1. Field of the Invention
The present invention relates to compressor-controlling device and method for an air conditioner comprising a plurality of compressors, and more particularly to compressor-controlling device and method for an air conditioner comprising a plurality of compressors, in which stopped compressors selected from the plural compressors are re-operated so as to satisfy an increased cooling load after a lapse of a designated time taken to equalize pressures at inlets and outlets of the stopped compressors.
2. Description of the Related Art
Generally, an air conditioner comprises a compressor for compressing a gaseous refrigerant in a low-temperature and low-pressure state so as to convert it into a high-temperature and high-pressure state, an outdoor heat exchanger for condensing the gaseous refrigerant in the high-temperature and high-pressure state compressed by the compressor so as to convert it into a liquid refrigerant in a mid-temperature and high-pressure state, an expansion device for decompressing the liquid refrigerant in the mid-temperature and high-pressure state condensed by the outdoor heat exchanger so as to convert it into a low-temperature and low-pressure state, and an indoor heat exchanger for evaporating the liquid refrigerant in the low-temperature and low-pressure state decompressed by the expansion device so as to convert it into a gaseous refrigerant in a low-temperature and low-pressure state.
Further, recently, the air conditioner employs a plurality of compressors having different capacities so as to variably change the total capacity of the operated compressors according to cooling loads, thereby properly satisfying the variation of the cooling load and optimizing cooling efficiency.
FIG. 1 is a block diagram of a conventional capacity variable air conditioner.
As shown in FIG. 1, the capacity variable air conditioner comprises first and second compressors 2 and 3, an outdoor heat exchanger 4, an expansion valve 6, and an indoor heat exchanger 8. The first and second compressors 2 and 3 compress a gaseous refrigerant in a low-pressure state so as to convert it into a high-temperature and high-pressure state. The outdoor heat exchanger 4 condenses the gaseous refrigerant compressed by the first and second compressors 2 and 3 so as to convert it into a liquid refrigerant in a mid-temperature and high-pressure state. The expansion valve 6 decompresses the liquid refrigerant condensed by the outdoor heat exchanger 4 so as to convert it into a gaseous or liquid refrigerant in a low-temperature and low-pressure state. The indoor heat exchanger 8 evaporates the refrigerant decompressed by the expansion valve 6 so as to convert it into a gaseous refrigerant in a low-temperature and low-pressure state.
An accumulator 10 for gasifying the liquid refrigerant is connected to inlets of the first and second compressors 2 and 3 so as to prevent the liquid refrigerant passing through the indoor heat exchanger 8 from flowing into the first and second compressors 2 and 3. First and second check valves 12 and 13 are respectively installed at each outlet of the first and second compressors 2 and 3 so as to prevent the refrigerant discharged from the first and second compressors 2 and 3 from flowing backward to the first and second compressors 2 and 3.
Herein, according to cooling loads, the first and second compressors 2 and 3 are simultaneously operated or selectively operated, thereby variably changing their total capacity.
Further, an overload protector (not shown; hereinafter, referred to as a xe2x80x9cOLPxe2x80x9d) is interposed between the first and second compressors 2 and 3. When a compressor in a suspension state is overloaded, the OLP serves to cut off power supplied to the stopped compressor. The OLP is turned on and off by heat generated by the stopped compressor in case the stopped compressor is re-operated when pressures at the inlet and the outlet of the stopped compressor are not equalized.
When the cooling load is decreased, parts of the plural compressors are stopped, and when the cooling load is increased and exceeds the total capacity of the operated compressors, the stopped compressors are re-operated.
However, in the conventional air conditioner, when the stopped compressors for satisfying the decreased cooling load are re-operated, if the stopper compressors are re-operated before pressures at the inlets and outlets of the stopped compressors are equalized, the stopped compressors are repeatedly overloaded by the pressure non-equilibrium. Therefore, the OLP is repeatedly driven, thereby causing difficulty in normally re-operating the stopped compressors.
Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide compressor-controlling device and method for an air conditioner comprising a plurality of compressors, in which stopped compressors for satisfying the decrease of a cooling load are re-operated after pressures at inlets and outlets of the stopped compressors are equalized, thereby normally re-operating the stopped compressors without an overload.
In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of a compressor-controlling device for an air conditioner comprising a plurality of compressors, comprising: a movable timer for sensing a stopping time (t) of stopped compressors selected from the plural compressors according to a decrease of a cooling load; a comparison unit for determining whether the stopping time (t) sensed by the movable timer exceeds a designated time (T); and a control unit for re-operating the stopped compressors after a lapse of the designated time (T) when the cooling load is increased, in case the comparison unit judges that the stopping time (t) does not exceed the designated time (T).
In accordance with another aspect of the present invention, there is provided a compressor-controlling method for an air conditioner comprising a plurality of compressors, comprising: the first step of selectively stopping parts of the plural compressors operated in a cooling mode according to a decrease of cooling load; and the second step of re-operating the stopped compressors of the first step after a lapse of a designated time (T) when the cooling load is increased so as to exceed a total capacity of the compressors operated in the first step.